The early morning overflow on a Beach Park road injured 37 people, according to the Chicago Tribune.

Investigators believe a tractor was hauling a pair of 2-ton tanks containing anhydrous ammonia when they began to leak, said Sgt. Christopher Covelli, a spokesman for the Lake County Sheriff’s Office. He added those probing the spill don’t believe the vehicle was involved in a traffic accident.

“Basically, it caused the substance to go airborne, which released the plume into the air, which is extremely dangerous," asserted Covelli. "The substance can reportedly cause unconsciousness, and, at worst case, even death.”

“Deputies arrived on the scene — our first responding deputies — (and they) exited their vehicles to try to aid the individuals who were at the scene, including individuals that were lying on the ground,” said Covelli.

The toxic cloud hovered over Beach Park for several hours and officials insisted residents within a 1-mile radius of the accident remain inside their homes and shut all windows, reported The Associated Press.

In all, 11 firefighters were injured, according to the Lake County Sheriff’s Office.

Motorist Pamela Burnett said she was on her way to work while driving through the toxic fog.

“It kept on getting bigger and bigger. This wasn’t going away,” Burnett told reporters Thursday at the scene. “The next thing I knew, I couldn’t breathe. It was such a strong smell. I thought to myself, ‘Lord, this is it. I’m done now.' ”